The Focusing Implementation to Bring Effective Reminders (FIBER) mixed-methods 4-year study will evaluate the implementation of a large-scale population-based colorectal cancer (CRC) screening patient reminder program and coordinated follow-up. FIBER will use the Practical Robust Implementation and Sustainability Model (PRISM), developed by the investigators, to guide the analyses. PRISM considers elements within the intervention design, external environment, intervention implementation and maintenance infrastructure, and characteristics of the adopting organization and its patients that are associated with program Reach, Effectiveness, Adoption, Implementation, and Maintenance (the RE-AIM evaluation framework). Primary aims: Among health plan members aged 50-80 who are due for colorectal cancer screening (n= 50,000);their primary care provider (PCP) teams (n=265);consulting specialists, and key staff (n=45);and key health care managers and staff (n=10) in 15 medical centers in Oregon and Washington: 1. To determine the Effectiveness and Maintenance of a CRC screening patient reminder program by conducting a practical randomized controlled trial (RCT) (n= 6000) to evaluate the short-term effect of program implementation on CRC screening and the cost per additional CRC screen, and using a longitudinal cohort study of CRC screening (n=44,000 patients not in the RCT) to estimate the longer- term effectiveness and costs of the program at the PCP team level. 2. To elucidate patient, PCP team, and system factors important to implementation success 3. To describe and explain the CRC screening patient reminder program Reach (to diverse patients), Effectiveness, Adoption, Implementation, and Maintenance, guided by the PRISM, to empower implementation improvements for further evaluation. 4. To create, refine, and disseminate an implementation guide for CRC screening reminder programs by combining the findings from Aims 1-3 and the perspectives from informant interviews of key staff at three future dissemination-implementation sites.